main.lisp: Change `filter` to use `remove-if-not`

Just learned about `remove-if-not`. Really cleans up this function. Not
even really necessary to keep `filter`, but I guess I'll hold on to it
for now.

1 files changed, 1 insertions, 6 deletions

diff --git a/l/src/main.lisp b/l/src/main.lisp
index 0689107..a75fbc3 100644
--- a/l/src/main.lisp
+++ b/l/src/main.lisp
@@ -94,9 +94,4 @@
     (filter #'extensionp targets)))
 
 (defun filter (predicate list-form)
-  (let ((newl '()))
-    (dolist (el list-form)
-      (if (funcall predicate el)
-          (push el newl)))
-
-    newl))
+  (remove-if-not predicate list-form))